theme 4a Flashcards
what is the blending theory of inheritance?
hereditary traits blend evenly in offspring through mixing of the parents’ blood
what is transmission genetics?
the field of genetics that deals with the way genetic differences among individuals are passed from generation to generation
what is the issue with the blending theory of inheritance?
if it were true, it would result in variation to be lost over time as extremes would only be produced when two organisms in the same extreme reproduce, which is unlikely
what did Gregor Mendel do?
- tested hypothesis of blending vs. particulate inheritance
- used true-breeding varieties of peas
what is a character?
a heritable characteristic, such as fur colour or seed shape. refers to the general category, not the type of characteristic itself (NOT brown fur colour)
what is a trait?
a variation in character, such as brown fur colour or round seed shape
what are P generations, F1 generations, and F2 generations?
P: parental.
F1: fillial, comes from P generation individuals reproducing with each other.
F2: offspring of the F1 generation
what is dominance?
the masking of one allele by a different “stronger” allele
what is the principle of segregation?
the idea that the pair of alleles that control a character separate as gametes are formed, so half the gametes contain one allele and the other half contain the other
what is a homozygote?
an individual homozygous for an allele (has two identical alleles for one gene)
what is a heterozygote?
an individual heterozygous for an allele (has two different alleles for one gene)
what is a monohybrid?
a heterozygote for a single character
what is a monohybrid cross?
a cross between two individuals that are both heterozygous for the pair of alleles
what are Mendel’s 3 hypotheses?
the genes that govern genetic characters are present in two copies in individuals
if different alleles are present in an individual’s pair of genes, one allele is dominant over the other
two alleles of a gene segregate and enter gametes separately (diploid organisms get one allele from each parent)
when is the probability product rules used?
for the probability of independent events occurring in succession (like the probability of rolling two 6s when rolling two dice at once)
when is the probability sum rule used?
for the probability of any one of several mutually exclusive events occurring
what is a testcross?
mating an individual with a dominant phenotype (but unknown genotype) to a recessive genotype to determine if it is homozygous dominant or heterozygous
what do the results of a testcross indicate?
if half the offspring display the recessive phenotype, the tested individual must be a heterozygote
if all offspring displaythe dominant phenotype then the tested individual must be a homozygote
what did Walter Sutton do? (general)
noticed parallels between Mendel’s principle of segregation and the behaviour of chromosomes during meiosis
what parallels did Sutton notice between chromosomes and Mendel’s principle of segregation?
chromosomes occur in pairs in diploid organisms
chromosomes of each pair are separated and delivered singly to gametes
separation of any pair of chromosomes in meiosis and gamete formation is independent of the separation of other pairs
what is the chromosomal theory of inheritance?
genes and their alleles are carried on chromosomes
what is a locus?
the particular site on a chromosome where a specific gene is located
what is incomplete dominance?
the phenotype of the heterozygous is an intermediate between the dominant and recessive homozygotes: the effects of recessive alleles can be detected to some extent in heterozygotes
how are alleles labelled when they display incomplete dominance?
use uppercase letter for character and a superscript to identify the trait (instead of lower and upper case letters)
